Glaucoma is a disease condition of the eye in which increased intraocular pressure (IOP) is created by dysfunction in the drainage mechanism for the aqueous humor. Aqueous humor is produced within the eye in the ciliary body and flows within the anterior region of the eye. The aqueous humor normally flows through a network of tissues at the interior angle of the anterior chamber, named the trabecular meshwork and subsequently into a circular drainage space named Schlemm's canal. The aqueous humor continues its drainage path into collector channels and finally into aqueous veins to enter the venous system.
Typically in open angle glaucoma, the pathway for aqueous humor becomes narrowed or occluded, increasing IOP and resulting in gradual nerve damage and loss of vision. Such conditions are usually treated by topical drugs in the form of eye drops, but may result in surgical treatment if drug treatment becomes ineffective or if patient compliance is an issue. Traditional glaucoma surgery, such as trabeculotomy or trabeculectomy, involves dissection of the eye and the forming of new holes through the trabecular meshwork portion of the drainage pathway. The fluid is channeled to a reservoir formed under the conjunctiva known as a bleb. While blebs are effective in removing the aqueous humor, bleb complications present the highest incidence of post-surgical complications due to irritation and infection.
A new class of surgical procedures aims to approach treatment of the ocular drainage system from the scleral tissues without penetrating the interior chamber of the eye. These procedures are termed “non-penetrating” surgery and involve careful surgical dissection of the scleral tissues to access the tissues involved with ocular drainage. Deep sclerectomy is a form of this type of procedure in which a portion of intrascleral tissue is removed nearly to Descemet's membrane to allow significant aqueous flow from the anterior chamber to a bleb. Viscocanalostomy is another non-penetrating procedure, which increases the flow of aqueous humor form the anterior chamber into a surgically created intrascleral lake. Although non-penetrating procedures present fewer direct complications than traditional surgeries, most of the procedures still require the surgical dissection of ocular tissues and a high level of surgical skill.
Various approaches and devices for glaucoma surgery involving the rerouting of aqueous humor have been described in the art. One approach involves the shunting of aqueous humor through a tube in the anterior chamber into a reservoir implanted on the surface of the eye. See Mendez U.S. Pat. No. 4,428,746, White U.S. Pat. No. 4,554,918, Molteno U.S. Pat. No. 4,750,901, Ahmed U.S. Pat. No. 5,071,408, U.S. Pat. No. 5,411,473, U.S. Pat. No. 5,616,118, U.S. Pat. No. 5,681,275, U.S. Pat. No. 5,785,674, U.S. Pat. No. 6,261,256, Baerveldt, et al. U.S. Pat. No. 5,178,604, U.S. Pat. Nos. 5,397,300, 5,558,629, 6,050,970, Speckman U.S. Pat. No. 5,338,291, Memmen U.S. Pat. No. 5,370,607, Jacob U.S. Pat. No. 5,882,327, Odrich U.S. Pat. No. 6,41,666. A similar approach is to shunt the aqueous humor through a tube placed in the anterior chamber into a bleb on the surface of the eye. See Worst U.S. Pat. No. 5,180,362, Suson U.S. Pat. No. 6,508,779, Wilcox WO 02/32343.
Another approach described in the art is the shunting of aqueous humor from the anterior chamber to the tear film of the eye. See Ungerleider U.S. Pat. No. 4,936,825; U.S. Pat. No. 5,372,577; Wandel U.S. Pat. No. 5,807,302; Brown U.S. Pat. No. 6,595,945.
Another approach described in the art is placing a shunt for aqueous humor through the trabecular meshwork to connect the anterior chamber and Schlemm's canal. See Lynch et al. U.S. Pat. No. 6,450,984, Hill U.S. Pat. No. 6,533,768, WO 01/78656, and Gharib et al. U.S. 2002 0165478.